[Gecko]

I think a Priority Speaker plugin would be a really good idea.

Priority Speaker

Priority users (defined by a permission flag) gain the Priority Speaker status.
When a Priority Speaker uses their mic, anybody else who is talking at the same time has their voice transmit volume lowered by x percent. If you've used Teamspeak before, it has the same concept.

Special users (defined by a separate permission flag) whose voices are never altered, even if a Priority Speaker is talking.

This would be good for server admins, so that they can administrate without needing to mute everybody else who is talking at the same time.

The VoiceHook extension might be of use in this, though I'm not sure if it has the capability of altering volume.

[KissLick]

Yep, this would be really nice!

[Horsedick]

This was brought up once before but the only thing I found to do as an Admin was two different ways to make it so whenever I pushed to speak in game in the server it auto muted everyone else till I took my finger off the button. You need a client side config file with the binds to make it happen...also to avoid spamming the chat box with me muting and unmuting everyone I just edited the print to chat out in the basecomm and recompiled it.

I have to update that file and redo it every so often if its updated by the SM team but either way it works pretty good.

[friagram]

There are sourcemod natives you can use to mute/unmite people to accomplish this